DISEASES CLOVEE SICKNESS." 117 



ploughed under. The fresh succulent roots are ramified 

 over a great extent of the superficies of the soil. If 

 clover is sown on the same land too frequently, the 

 young roots, coming in contact with the decaying remains 

 of the former crop, may be attacked by mildew ; or more 

 probably the rootlets do not exercise their functions in a 

 healthy manner, and failing to take up a proper quantity 

 of earthy matter, render the plant weak and sickly. When 

 in this state mildew or insects may attack the plant, and 

 complete its destruction." The presence of fungi is gene- 

 rally considered as indicative of the existence rather than 

 the cause of disease : they are only present when the health 

 of the structure has been impaired by other influences. Mr. 

 Russell further observes, "that the presence of certain 

 kinds of decaying vegetable matter weakens the constitu- 

 tions of those plants that require a change of soil, by inter- 

 fering with the absorbing powers of their roots. These are 

 rendered unable to dissolve and absorb the food which is 

 diffused through the mass of the soil, and as a consequence, 

 assimilation does not take place in a healthy manner; 

 the fluids circulating in the vessels of the plants not being 

 in a sound state, become a fit nidus either for the growth 

 of fungi or the attacks of insects." As Mr. Berkeley ob- 

 serves, "The clover roots are rarely found having any 

 unhealthy appearance about them. The disease is first 

 seen in the leaves, and afterwards extends to the parts 

 below the surface. The upper parts of the plant, being 

 more exposed to all the variations of the atmosphere, are 

 the first to give way when the constitution of the plant is 

 weakened by other causes. In some cases infection may 

 result from contact with decaying matter ; but we consider 

 that the evidence favours the view of the diseased condi- 

 tions arising from the want of proper nutriment being 

 taken up by the roots/' 



Here we have the opinions of two competent men, 



